The abstract of that PCT specification PCT/NZ99/00186 (published as WO 00/45068) described one example of a Continuously Variable Transmission. That abstract was based on various configurations including that shown in FIG. 10, and said: A transmission is provided which comprises a fixed housing or support 105, input means 121, 156 moveable relative to said support and a torque shaft 112 rotatable about its longitudinal axis and a driven shaft arranged to be rotated about its longitudinal axis by the torque shaft 112, a first one-way clutch 102 between the torque shaft 112 and driven shaft 104, linkage means 117, 134, 135, 132, 140, 147, 158, 170 rotatable about the axis of rotation of the driven shaft 104 under the influence of said input means 121 and an inertial body 113, 160 mounted on the linkage means to be cyclically angularly deflected in response to the input means, the reaction forces generated by the inertial body 113, 160 as it is cyclically deflected being applied to the torque shaft 112 as positive and negative torque and the torque shaft 112 being connected over a second one-way clutch 101 opposite to the first one-way clutch 102 either to said support 105 or to the driven shaft 104 over a rotation reversal system 150, 151, 152 whereby the drive shaft 155 can be rotated by the torque shaft 112 in one sense of rotation only. The inertial body preferably comprises a rotor 113 so that gyroscopic forces are applied to the torque shaft 112.
Various methods were described in said PCT application to generate and control the output torque. The methods described to spin the rotor varied from using an independent source to drive the rotor, to driving the rotor from the transmission input using gear trains and a one-way clutch.
The main method described to control the output torque involved controlling the independent source driving the rotor. Therefore when it is desired to maintain the input speed within narrow limits the only option left would be an independent source to drive the rotor to control the output torque by controlling the rotor speed.
The method of driving the rotor by an independent source such as an electric motor, while it is attractive poses challenges such as access to power supply, motor construction to withstand complex dynamic conditions and operating environment and therefore a subject for future development.
The method of driving the rotor by the input rotation through gear trains and one-way clutch, while it may be satisfactory for non-differential type configurations poses problems when used for differential type configurations as described in FIG. 10. This is due to the relatively high loadings on the rotor drive gear train caused by the accelerations and decelerations of the sub-frame that carry the rotor. The differential type configuration is preferred in many applications due to compactness, dynamic balancing etc.